Endemic carbapenem-resistant Acinetobacter species in Brooklyn, New York: citywide prevalence, interinstitutional spread, and relation to antibiotic usage

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

Acinetobacter baumannii Carbapenemase Producers in Morocco: Genetic Diversity

INTRODUCTION

 Carbapenem resistance in Acinetobacter baumannii (A. baumannii) is a public health problem worldwide. Although carbapenem resistance is emerging in Morocco, few studies have shown the epidemiological profile of carbapenemase genes in Moroccan healthcare facilities. The aim of this study was to characterize the molecular profile of the carbapenemase enzyme in Acinetobacter baumannii from clinical isolates.

METHODS

Clinical strains isolated in the laboratory from various samples were subjected to several phenotypic tests. Antibiotic susceptibility and identification were tested using Phoenix 100 (Becton Dickinson Co., Sparks, MD, USA) and Api 20 (bioMérieux, Marcy-l'Etoile, France). Simple phenotypic assays were used to detect carbapenemase oxacillinase (OXA) and metallo-β-lactamase (MBL) production, including the modified Hodge test (MHT) and ethylenediaminetetraacetic acid (EDTA) test. The detection of carbapenemase genes was performed by multiplex and simple polymerase chain reaction (PCR).

RESULTS

A total of 140 strains or 100% of isolates contained OXA-51 and ISbA1 sequences, 89% contained OXA-23 and OXA-58 sequences, and 1% contained OXA-24 sequence. The MBL genes were predominated by Verona integron-encoded metallo-β-lactamase (VIM) (56%), followed by Seoul imipenemase (SIM) (39%), German imipenemase (GIM) (37%), São Paulo metallo-β-lactamase (SPM) (13%), imipenemase (IMP) (11%), and New Delhi metallo-β-lactamase (NDM) (4%). Guyana extended-spectrum β-lactamase (GES) was not found in any isolation.

CONCLUSION

Our study shows a high frequency of carbapenem resistance in Acinetobacter baumannii, as it reports a high molecular diversity of carbapenemase-encoding genes, mainly dominated by the carbapenemase ISaba1/OXA-23, which represents an emerging threat in our hospital.

A systematic review and meta-analysis for risk factor profiles in patients with resistant Acinetobacter baumannii infection relative to control patients

BACKGROUND

Acinetobacter baumannii is a major cause of nosocomial infections and high mortality rates. Evaluation of risk factors for such resistant infections may aid surveillance and diagnostic initiatives, as well as, can be crucial in early and appropriate antibiotic therapy.

OBJECTIVE

To identify the risk factors in patients with resistant A. baumannii infection with respect to controls.

METHODS

Prospective or retrospective cohort and case-control studies reporting the risk factors for resistant A. baumannii infection were collected through two data sources, MEDLINE/PubMed and OVID/Embase. Studies published in the English language were included while animal studies were excluded. The Newcastle-Ottawa Scale was used to assess the quality of studies. The odds ratio of developing antibiotic resistance in patients with A. baumannii infection was pooled using a random-effect model.

RESULTS

The results are based on 38 studies with 60878 participants (6394 cases and 54484 controls). A total of 28, 14, 25, and 11 risk factors were identified for multi-drug resistant (MDRAB), extensive-drug resistant (XDRAB), carbapenem-resistant (CRAB) and imipenem resistant A. baumannii infection (IRAB), respectively. In the MDRAB infection group, exposure to carbapenem (OR 5.51; 95% CI: 3.88-7.81) and tracheostomy (OR 5.01; 95% CI: 2.12-11.84) were identified with maximal pool odd's ratio. While previous use of amikacin (OR 4.94; 95% CI: 1.89-12.90) and exposure to carbapenem (OR 4.91; 95% CI: 2.65-9.10) were the foremost factors associated with developing CRAB infection. Further analysis revealed, mechanical ventilation (OR 7.21; 95% CI: 3.79-13.71) and ICU stay (OR 5.88; 95% CI: 3.27-10.57) as the most significant factors for XDRAB infection.

CONCLUSION

The exposure of carbapenem, amikacin (previous) and mechanical ventilation were the most significant risk factors for multidrug, extensive-drug, and carbapenem resistance in patients with A. baumannii infection respectively. These findings may guide to control and prevent resistant infections by identifying the patients at higher risk of developing resistance.

Infection control measures to stop the spread of sequence type 15 OXA-23-producing Acinetobacter baumannii in a Swedish Burn Center

OBJECTIVE

To describe the course of the outbreak and infection control measures to stop the spread of sequence type 15 OXA-23-producing Acinetobacter baumannii in the Burn Center of Uppsala University Hospital, between November 2014 and the end of April 2015.

METHODS

Compliance with hand hygiene, dress code, and cleaning routines were reviewed, the ward's environment was systematically investigated to identify potential environmental sources. Sampling routines for A. baumannii, from patients and environment, were established, and the epidemiological relationship was analysed for all carbapenem-resistant A. baumannii isolates using arbitrarily primed polymerase chain reaction (AP-PCR) and pulsed-field gel electrophoresis (PFGE).

RESULTS

A total of 54 patients were treated at the burn intensive care unit during the studied, approximately five months period, and an OXA-23-producing A. baumannii was isolated from nine patients (9/54, 17%), whereof two died (2/9, 22.2%). All isolates shared identical PFGE-genotype patterns and belonged to sequence type 15; AP-PCR was eligible for prompt epidemiological investigations.

CONCLUSIONS

Higher awareness and increased compliance with hand hygiene and dress code as well as intensified cleaning protocols of the environment and equipment were successfully established and likely to have led to stop the spread of sequence type 15 OXA-23-producing Acinetobacter baumannii.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Prevalence of High-Risk Antibiotic Resistant Acinetobacter baumannii in the Holy Cities of Makkah and Al-Madinah

Background:

Acinetobacter baumannii strains resistant to carbapenems are a global public health problem.

Objectives:

The aim of the present study is to evaluate the prevalence of genetic fingerprints associated with Metallo β-lactamases in A. baumannii in addition to the clonal diversity of A. baumannii in Makkah and Al-Madinah regions of Saudi Arabia, which receive a high number of international visitors.

Methods:

Multi-antibiotic resistant A. baumannii isolates were investigated. Bacterial isolation was conducted employing a basic bacteriological technique after confirming the ID of isolates. The antimicrobial susceptibility test was carried out using the Vitek 2 compact system. The molecular clonal diversity of the isolates was determined by Pulse Field Gel Electrophoresis (PFGE). Clusters were analyzed with BioNumerics software version 6.5. Dice coefficient was used for calculating the similarities.

Results:

The results indicated resistance in 82.5% of A. baumannii isolates against the carbapenems. All the isolates were found to be sensitive to colistin, while 5% of isolates were resistant to tigecycline. The screening of carbapenem-resistant A. baumannii isolates showed that the dissemination of imipenem and meropenem resistance was 81 and 84%, respectively, while the majority of the strains were susceptible to tigecycline and colistin. The blaOXA and blaVIM were the most encountered genes in A. baumannii isolates, while ISAba1 was the prominent insertion sequence. The genetic fingerprinting results (PFGE) revealed two types of epidemic clones: monoclonal and polyclonal models of 17 clusters.

Conclusion:

The current investigation indicates the diversity in genetic fingerprints of carbapenem-resistant A. baumannii in Makkah and Al-Madinah region of Saudi Arabia, and that two types of epidemic clones are present. It has also been demonstrated that such clones create serious infection dissemination to other parts of the world as heavy pilgrimage traffic is received throughout the year in Makkah and Al-Madinah, especially in the Haj season.

Association of capsular polysaccharide locus 2 with prognosis of Acinetobacter baumannii bacteraemia

Acinetobacter baumannii causes healthcare-associated infections worldwide. Capsular polysaccharide (CPS) is shown an important virulence factor of A. baumannii both in vitro and in vivo. Capsule locus 2 (KL2) for CPS is the most common KL type and is associated with carbapenem resistance. It is unclear whether KL2 is related to the clinical outcome of invasive A. baumannii infection. Here we had followed patients with A. baumannii bacteraemia prospectively between 2009 and 2014. One-third of the unduplicated blood isolates were randomly selected each year for microbiological and clinical studies. The KL2 gene cluster was identified using polymerase chain reaction. A total of 148 patients were enrolled randomly. Eighteen isolates (12.2%) carried KL2, and 130 isolates (87.8%) didn’t. Compared with non-KL2 isolates, KL2 isolates had significantly higher resistance to imipenem, sulbactam, and tigecycline. Compared with the non-KL group, in the KL2 group, the hospital stay before development of bacteraemia was longer (P < 0.001), a higher percentage had pneumonia (P = 0.004), and the white blood cell count was lower (P = 0.03). Infection with KL2 A. baumannii predicted mortality (adjusted hazard ratio [aHR], 2.03; 95% confidence interval [CI], 1.09–3.78; P = 0.03), independently of the Pitt bacteraemia score (aHR, 1.34; 95% CI, 1.23–1.46; P < 0.001) and leucopenia (aHR, 2.16; 95% CI, 1.30–3.57; P = 0.003). Thrombocytopenia contributed to the effect of KL2 on mortality in bacteraemia (Sobel test P = 0.01). Large-scale studies are warranted to confirm these findings and the underlying mechanisms deserve further investigation.

Fatty Acid Composition, Antioxidant, and in vitro Anti-inflammatory Activity of Five Cold-Pressed Prunus Seed Oils, and Their Anti-biofilm Effect Against Pathogenic Bacteria

Background/Aim: Sweet almond (Prunus amygdalus dulcis) oil is one of the most famous cold-pressed seed oils. However, other species of Prunus can provide oils with healthy properties. We analyzed the fatty acid (FA) composition, as well as the antioxidant, the in vitro anti-inflammatory properties, and the antibiofilm activity of five commercial vegetable cold-pressed seed oils of apricot, peach, plum, cherry, and black cherry. Methods: Gas Chromatography-Mass Spectrometry was performed for the analysis of FAs The antioxidant property of the oils was carried using different tests [2, 2-diphenyl-1-picrylhydrazyl (DPPH assay)], Ferric Reducing Antioxidant Power (FRAP), and the 2, 20 -azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·+). The denaturation assay performed on bovine serum albumin (BSA) was used to evaluate the in vitro anti-inflammatory activity. The anti-biofilm activity was assessed using five pathogenic strains, namely, Acinetobacter baumannii, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus, through the crystal violet test and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), used to evaluate the metabolism of the microbial cells present within the biofilm. Results: Oleic acid and linoleic acids were the most abundant FAs. Black cherry seed oil exhibited the best antioxidant activity, but in general, the amount of oil needed to inhibit the activity of 1 ml of DPPH assay at 50% did not exceed 10 μg. The extract concentration for the 50% inhibition of the denaturation of the protein (IC50) did not exceed 4.4 μg. Linoleic and stearic acids affected the antioxidant activity of the oils; oleic acid, linolenic, and palmitoleic acids exhibited beneficial effects in preserving the BSA denaturation, as shown by the correlation data. The oils were able to inhibit the biofilm formation of the pathogens (up to 71.40% of inhibition) as well as act against their mature biofilm, although with different strengths, with values up to 61.54%. Concurrently, they also acted on the pathogen metabolism. Conclusion: The oils represent a valuable source of some healthy FAs. They showed potential antioxidant and anti-inflammatory in vitro activity, in addition, their potential effect on the biofilm can offer important ideas for research and reflection on their use as functional foods and/or ingredients.

Mapping Global Prevalence of Acinetobacter baumannii and Recent Vaccine Development to Tackle It

Acinetobacter baumannii is a leading cause of nosocomial infections that severely threaten public health. The formidable adaptability and resistance of this opportunistic pathogen have hampered the development of antimicrobial therapies which consequently leads to very limited treatment options. We mapped the global prevalence of multidrug-resistant A. baumannii and showed that carbapenem-resistant A. baumannii is widespread throughout Asia and the Americas. Moreover, when antimicrobial resistance rates of Acinetobacter spp. exceed a threshold level, the proportion of A. baumannii isolates from clinical samples surges. Therefore, vaccines represent a realistic alternative strategy to tackle this pathogen. Research into anti-A. baumannii vaccines have enhanced in the past decade and multiple antigens have been investigated preclinically with varying results. This review summarises the current knowledge of virulence factors relating to A. baumannii–host interactions and its implication in vaccine design, with a view to understanding the current state of A. baumannii vaccine development and the direction of future efforts.

The Role of Uniform Meropenem Usage in Acinetobacter baumannii Clone Replacement

The dominant carbapenem resistant Acinetobacter baumannii harboring bla_OXA-23-like carbapenemase was replaced by bla_OXA-40-like carriers in a Hungarian tertiary-care center with high meropenem but relatively low imipenem use. We hypothesized that alterations in antibiotic consumption may have contributed to this switch. Our workgroup previous study examined the relation between resistance spiral and the antibiotic consumption, and the results suggest that the antibiotic usage provoked the increasing resistance in case of A. baumannii. We aimed at measuring the activity of imipenem and meropenem to compare the selection pressure exerted by the different carbapenems in time-kill assays. Strain replacement was confirmed by whole genome sequencing, core-genome multilocus sequence typing (cgMLST), and resistome analysis. Based on results of the time-kill assays, we found a significant difference between two different sequence-types (STs) in case of meropenem, but not in case of imipenem susceptibility. The newly emerged ST636 and ST492 had increased resistance level against meropenem compared to the previously dominant ST2 and ST49. On the other hand, the imipenem and colistin resistance profiles were similar. These results suggest, that the uniform meropenem usage may have contributed to A. baumannii strain replacement in our setting.

Acinetobacter spp. in food and drinking water - A review

Acinetobacter spp. has emerged as a pathogen of major public health concern due to their increased resistance to antibiotics and their association with a wide range of nosocomial infections, community-acquired infections and war and natural disaster-related infections. It is recognized as a ubiquitous organism however, information about the prevalence of different pathogenic species of this genus in food sources and drinking water is scarce. Since the implementation of molecular techniques, the role of foods as a source of several species, including the Acinetobacter baumannii group, has been elucidated. Multidrug resistance was also detected among Acinetobacter spp. isolated from food products. This highlights the importance of foods as potential sources of dissemination of Acinetobacter spp. between the community and clinical environments and reinforces the need for further investigations on the potential health risks of Acinetobacter spp. as foodborne pathogens. The aim of this review was to summarize the published data on the occurrence of Acinetobacter spp. in different food sources and drinking water. This information should be taken into consideration by those responsible for infection control in hospitals and other healthcare facilities.

High Frequency of AdeA, AdeB and AdeC Genes among Acinetobacter baumannii Isolates

BACKGROUND

Efflux pumps are involved in resistance of Acinetobacter baumannii isolates to antimicrobial agents. AdeABC efflux pump is one of the RND superfamily efflux pump and consists of adeA (membrane fusion), adeB (multidrug transporter) and adeC (outer membrane) genes. In this study, the frequency of adeA, adeB and adeC genes among A. baumannii isolates with resistance to erythromycin, trimethoprim, meropenem and imipenem was investigated.

METHODS

Overall, 79 strains of A. baumannii were isolated from patients admitted to two major hospitals in Tehran during 2016. Antibiotic susceptibility testing was determined by disc diffusion and microdilution methods according to Clinical and Laboratory Standards Institute (CLSI) guideline. The presence of adeA, adeB and adeC genes was also determined using Multiplex PCR assay.

RESULTS

The highest and the lowest resistance among A. baumannii isolates were to trimethoprim (93%) and erythromycin (53%), respectively. The frequency of adeA, adeB and adeC genes was 96.2%, 96.2% and 91.1 % respectively. There was a significant relationship between imipenem resistance and presence of efflux pump genes (P<0.05).

CONCLUSION

According to the high prevalence of the AdeABC efflux system genes, it may involve in resistance of clinical isolates of A. baumannii to imipenem, especially.

Control and management of multidrug resistant Acinetobacter baumannii: A review of the evidence and proposal of novel approaches

Hospital-acquired infections are on the rise and are a substantial cause of clinical and financial burden for healthcare systems. While infection control plays a major role in curtailing the spread of outbreak organisms, it is not always successful. One organism of particular concern is Acinetobacter baumannii, due to both its persistence in the hospital setting and its ability to acquire antibiotic resistance. A. baumannii has emerged as a nosocomial pathogen that exhibits high levels of resistance to antibiotics, and remains resilient against traditional cleaning measures with resistance to Colistin increasingly reported. Given the magnitude and costs associated with hospital acquired infections, and the increase in multidrug-resistant organisms, it is worth re-evaluating our current approaches and looking for alternatives or adjuncts to traditional antibiotics therapies. The aims of this review are to look at how this organism is spread within the hospital setting, discuss current treatment modalities, and propose alternative methods of outbreak management.

Clinico-epidemiological profile of Acinetobacter and Pseudomonas infections, and their antibiotic-resistant pattern in a tertiary care center, Western Nepal

Background:

Infections caused by Acinetobacter species and Pseudomonas species, especially multidrug-resistant (MDR) strains pose a serious management challenge with a public health threat.

Materials and Methods:

A hospital-based retrospective study of patients who were infected with Acinetobacter spp or Pseudomonas aeruginosa was carried out at Manipal Teaching Hospital from 2014 to 2016.

Results:

A total of 170 cases of infections with Acinetobacter spp. and 313 cases with Pseudomonas aeruginosa were studied. The rate of nosocomial infections was higher than non-nosocomial infections. ICU was found as the major hub for both the organisms; (53.5% of cases due to Acinetobacter spp. and 39.6% due to Pseudomonas aeruginosa). Most isolates were of respiratory tract origin (Acinetobacter 74.7% and Pseudomonas aeruginosa 65.8%). Percentage resistance of Acinetobacter spp. towards polymyxin B was found to be quite low (18.8%). Similarly, resistance rates of Pseudomonas aeruginosa against amikacin were also found to be low, i.e., 17.4%. A higher prevalence of multidrug resistance was seen among Acinetobacter spp than among Pseudomonas aeruginosa (75.9% vs. 60.1%). The hospital stay was longer for patients infected with MDR isolate (p=0.001 for Acinetobacter spp. and p=0.003 for Pseudomonas aeruginosa). The mortality rate was higher in infections due to Acinetobacter spp (15.9%) as compared to Pseudomonas aeruginosa (8.3%).

Conclusion:

This study reveals that infections caused by Acinetobacter species and Pseudomonas aeruginosa are associated with prolonged hospital stay and high in-hospital mortality. These emphasize the need for prudent use of antibiotics and aggressive infection control strategies.

In situ identification of Gram-negative bacteria in human lungs using a topical fluorescent peptide targeting lipid A

Respiratory infections in mechanically ventilated patients caused by Gram-negative bacteria are a major cause of morbidity. Rapid and unequivocal determination of the presence, localization, and abundance of bacteria is critical for positive resolution of the infections and could be used for patient stratification and for monitoring treatment efficacy. Here, we developed an in situ approach to visualize Gram-negative bacterial species and cellular infiltrates in distal human lungs in real time. We used optical endomicroscopy to visualize a water-soluble optical imaging probe based on the antimicrobial peptide polymyxin conjugated to an environmentally sensitive fluorophore. The probe was chemically stable and nontoxic and, after in-human intrapulmonary microdosing, enabled the specific detection of Gram-negative bacteria in distal human airways and alveoli within minutes. The results suggest that pulmonary molecular imaging using a topically administered fluorescent probe targeting bacterial lipid A is safe and practical, enabling rapid in situ identification of Gram-negative bacteria in humans.

Epidemiology and Mechanisms of Resistance of Extensively Drug Resistant Gram-Negative Bacteria

Antibiotic resistance has increased markedly in gram-negative bacteria over the last two decades, and in many cases has been associated with increased mortality and healthcare costs. The adoption of genotyping and next generation whole genome sequencing of large sets of clinical bacterial isolates has greatly expanded our understanding of how antibiotic resistance develops and transmits among bacteria and between patients. Diverse mechanisms of resistance, including antibiotic degradation, antibiotic target modification, and modulation of permeability through the bacterial membrane have been demonstrated. These fundamental insights into the mechanisms of gram-negative antibiotic resistance have influenced the development of novel antibiotics and treatment practices in highly resistant infections. Here, we review the mechanisms and global epidemiology of antibiotic resistance in some of the most clinically important resistance phenotypes, including carbapenem resistant Enterobacteriaceae, extensively drug resistant (XDR) Pseudomonas aeruginosa, and XDR Acinetobacter baumannii. Understanding the resistance mechanisms and epidemiology of these pathogens is critical for the development of novel antibacterials and for individual treatment decisions, which often involve alternatives to β-lactam antibiotics.

Efficacy of bacteriophage treatment against carbapenem-resistant Acinetobacter baumannii in Galleria mellonella larvae and a mouse model of acute pneumonia

Background

Acinetobacter baumannii is an opportunistic pathogen that causes serious nosocomial infection in intensive care units. In particular, carbapenem-resistant A. baumannii (CRAB) strains have been increasing in the past decade, and they have caused major medical problems worldwide. In this study, a novel A. baumannii lytic phage, the YMC 13/03/R2096 ABA BP (phage Βϕ-R2096), which specifically causes the lysis of CRAB strains, was characterized in detail in vitro and in silico, and the in vivo effectiveness of phage therapy was evaluated using Galleria mellonella and a mouse model of acute pneumonia.

Results

The A. baumannii phage Βϕ-R2096 was isolated from sewage water using CRAB clinical strains selected from patients at a university hospital in South Korea. The complete genome of the phage Βϕ-R2096, which belongs to the Myoviridae family, was analyzed. Phage Βϕ-R2096 inhibited bacterial growth in a dose-dependent manner and exhibited high bacteriolytic activity at MOI = 10. In the evaluation of its therapeutic potential against CRAB clinical isolates using two in vivo models, phage Βϕ-R2096 increased the survival rates of both G. mellonella larvae (from 0 to 50% at 24 h) and mice (from 30% with MOI = 0.1 to 100% with MOI = 10 for 12 days) in post-infection of CRAB. In particular, phage Βϕ-R2096 strongly ameliorated histologic damage to infected lungs, with bacterial clearance in the lungs observed on day 3 postinfection in the mouse acute pneumonia model. Moreover, in vivo studies revealed no mortality or serious side effects in phage-treated groups.

Conclusion

The results of this study strongly suggest that phage Βϕ-R2096, a novel A. baumannii lytic phage, could be an alternative antibacterial agent to control CRAB infections. This study is the first report to compare in vivo evaluations (G. mellonella larvae and a mouse acute pneumonia model) of the therapeutic efficacy of a phage against CRAB infections.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1443-5) contains supplementary material, which is available to authorized users.

Trimethoprim-sulfamethoxazole vs. colistin or ampicillin-sulbactam for the treatment of carbapenem-resistant Acinetobacter baumannii: A retrospective matched cohort study

OBJECTIVES

This study aimed to assess the effectiveness of trimethoprim-sulfamethoxazole (TMP/SMX) as monotherapy for the treatment of carbapenem-resistant Acinobacter baumannii (A. baumannii) (CRAB) infections.

METHODS

This retrospective cohort study included patients receiving TMP/SMX as the main treatment for severe infections caused by CRAB, who were matched with patients treated with colistin or ampicillin-sulbactam (AMP/SUL) by age, Charlson score, department, and source of infection. Outcomes were compared among all patients and in a subgroup of propensity-score (PS) matched patients. The PS matching was performed using a match tolerance of 0.15 with replacement.

RESULTS

Fifty-three patients treated with TMP/SMX and 83 matched patients treated with colistin or AMP/SUL were included. Variables that were independently significantly associated with TMP/SMX treatment included admission for infection and septic shock, while abnormal cognition on admission and intensive care unit admission were associated with colistin or AMP/SUL treatment. All-cause 30-day mortality was lower with TMP/SMX compared with the comparator antibiotics among all patients (24.5%, 13 of 53 vs. 38.6%, 32 of 83, P=0.09) and in the PS-matched subgroup (29%, 9 of 31 vs. 55.2% 16 of 29, P=0.04). Treatment failure rates were not significantly different overall (34%, 18 of 53 vs. 42.4%, 35 of 83, P=0.339) and in the PS-matched subgroup (35.5%, 11 of 31 vs. 44.8%, 13 of 29, P=0.46). Time to clinical stability and hospitalization duration were significantly shorter with TMP/SMX. Patients treated with TMP/SMX probably had less severe infections than those treated with other antibiotics, even after matching.

CONCLUSIONS

TMP/SMX might be a valuable treatment option for TMP/SMX-susceptible CRAB infections. Given the very limited available treatment options, further studies assessing its effectiveness and safety are necessary.

Incidence, risk factors, and outcome of multidrug-resistant Acinetobacter baumannii acquisition during an outbreak in a burns unit

BACKGROUND

Multidrug-resistant Acinetobacter baumannii (MR-AB) can cause outbreaks in a burns unit.

AIM

To study the incidence, risk factors and outcome of MR-AB colonization during an outbreak.

METHODS

A prospective study was conducted from April to November 2014 in a burns unit in Paris. Weekly surveillance cultures of patients and their environment were performed. MR-AB acquisition, discharge, or death without MR-AB colonization were considered as competing events. To identify risk factors for colonization, baseline characteristics and time-dependent variables were investigated in univariate and multivariate analyses using Cox models. MR-AB strains were genotypically compared using multi-locus sequence typing.

FINDINGS

Eighty-six patients were admitted in the burns unit during the study period. Among 77 patients without MR-AB colonization at admission, 25 (32%) acquired MR-AB with a cumulative incidence of 30% at 28 days (95% CI: 20-40). Median time to MR-AB acquisition was 13 days (range: 5-34). In multivariate analysis, risk factors for MR-AB acquisition were ≥2 skin graft procedures performed [hazard ratio (HR): 2.97; 95% confidence interval (CI): 1.10-8.00; P = 0.032] and antibiotic therapy during hospitalization (HR: 4.42; 95% CI: 1.19-16.4; P = 0.026). A major sequence type of MR-AB (ST2) was found in 94% and 92% of patients and environmental strains, respectively, with all strains harbouring the blaOXA-23 gene. MR-AB colonization increased length of hospitalization (HR: 0.32; 95% CI: 0.17-0.58; P = 0.0002) by a median of 12 days.

CONCLUSION

A high incidence of MR-AB acquisition was seen during this outbreak with most strains from patients and their environment belonging to single sequence type. MR-AB colonization was associated with more skin graft procedures, antibiotic use, and prolonged hospitalization.

Genotypic diversity among multidrug resistant Pseudomonas aeruginosa and Acinetobacter species at Mulago Hospital in Kampala, Uganda

BACKGROUND

Multidrug resistant Pseudomonas aeruginosa and Acinetobacter species are common causes of nosocomial infections worldwide. Recently we reported the occurrence of carbapenem resistant Enterobacteriaceae, P. aeruginosa and Acinetobacter species at Mulago National Referral Hospital in Kampala, Uganda, but the isolates were not analyzed for genetic relatedness. Herein we report the intra-species genotypic diversity among P. aeruginosa and Acinetobacter baumannii isolated from hospitalized patients and the environment at Mulago Hospital, using repetitive elements-based PCR (Rep-PCR) genotyping.

RESULTS

A total of 736 specimens from hospitalized patients were processed for culture and sensitivity testing yielding 9 (1.2%) P. aeruginosa and 7 (0.95%) A. baumannii. Similarly, 100 samples from the hospital environment were processed yielding 33 (33%) P. aeruginosa and 13 (13%) A. baumannii. Altogether, 62 non-repetitive isolates were studied (42 P. aeruginosa and 20 A. baumannii), of which 38% (16/42) P. aeruginosa and 40% (8/20) A. baumannii were multidrug resistant (isolates resistant to three or more classes of antimicrobials). Carbapenem resistance prevalence was 33 and 21% for P. aeruginosa from patients and the environment, respectively, while it was 14 and 86% for A. baumannii from patients and environment, respectively. Cluster analysis of the Rep-PCR fingerprints revealed a high level of genetic diversity among the isolates within each species as few isolates were clustered (at 100% level of similarity). More to this, the clustered isolates revealed a complex nature of multidrug resistant P. aeruginosa and A. baumannii clones circulating at Mulago Hospital. Importantly, certain isolates from the environment and patients were clustered, implying that hospitalized patients at Mulago were probably infected with strains from the environment.

CONCLUSIONS

The prevalence of multidrug resistant P. aeruginosa and A. baumannii is high at Mulago Hospital but carbapenem resistance prevalence remains relatively low in isolates from hospitalized patients. Importantly, the prevalence of carbapenem resistance in isolates from the environment is high implying the infection control practices at the hospital might be inadequate.

Efficacy and toxicity of high-dose nebulized colistin for critically ill surgical patients with ventilator-associated pneumonia caused by multidrug-resistant Acinetobacter baumannii

PURPOSE

Few studies have compared nebulized and intravenous (IV) colistin for multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa pneumonia. This study compared the nephrotoxicity and clinical outcomes for these two delivery routes.

METHODS

This study retrospectively compared 95 critically ill surgical patients who were diagnosed with Acinetobacter baumannii ventilator associated pneumonia and received colistin between March 2013 and January 2016.

RESULTS

The most common diagnoses were brain hemorrhage (27.4%), traumatic brain injury (20%), traumatic thoracic injury (15.8%), and secondary peritonitis (11.6%). Compared to the IV group, the nebulizer group was significantly older (60.0 vs. 67.5years, p=0.010), had higher APACHE II scores (16.3 vs. 19.9, p=0.001), and more frequently had diabetes mellitus (6.8% vs. 21.6%, p=0.043). Nephrotoxicity was more common in the IV group (60.5% vs. 15.7%, p<0.0001). Both groups had similar microbiological and clinical outcomes (p=0.921 and p=0.719, respectively). Patients with nephrotoxicity exhibited prolonged IV or nebulized colistin treatment and more frequent combination with vancomycin. Nephrotoxicity was independently associated with IV delivery (odds ratio: 8.48, 95% confidence interval: 2.95-24.39, p<0.0001).

CONCLUSIONS

Nebulized colistin may have less nephrotoxicity and provide similar clinical results, compared to IV colistin.

Polymyxin B and Doxycycline Use in Patients with Multidrug-Resistant Acinetobacter baumannii Infections in the Intensive Care Unit

Background:

Multidrug-resistant Acinetobacter baumannii (MDR-Ab) has emerged as an increasingly problematic cause of hospital-acquired infections in the intensive care unit (ICU). MDR-Ab is resistant to most standard antimicrobials but often retains susceptibility to polymyxin B and doxycycline.

Objective:

To evaluate the efficacy and toxicity of polymyxin B and doxycycline in the treatment of MDR-Ab infections.

Methods:

A retrospective chart review was conducted between March 2002 and May 2005 in patients who received doxycycline or polymyxin B for treatment of MDR-Ab infections in ICUs within Grady Memorial Hospital, Atlanta, GA.

Results:

Thirty-seven patients with MDR-Ab infections were treated with polymyxin B or doxycycline. Median age was 41 years and median ICU length of stay was 18 days prior to acquisition of MDR-Ab. Clinical cure was observed in 22 of 29 (76%) evaluable patients treated with polymyxin B and 2 of 4 (50%) patients treated with doxycycline. In patients with follow-up cultures, microbiological cure was observed in 17 of 21 (81%) patients treated with polymyxin B and 2 of 3 (67%) patients treated with doxycycline. Nephrotoxicity developed in 21% (7 of 33) of patients who received polymyxin B. Neurotoxicity was observed in 2 (6%) patients who received polymyxin B. No adverse reactions were observed with doxycycline. Overall, crude mortality was 27% (9 of 33) and 75% (3 of 4) among those who received polymyxin B and doxycycline, respectively. Three (9%) deaths were attributed to polymyxin B treatment failure, and no deaths were attributed to doxycycline treatment failure.

Conclusions:

Polymyxin B was effectively used to treat a substantial proportion of critically ill patients with MDR-Ab infection and was associated with a similar rate of nephrotoxicity as previously reported. Doxycycline monotherapy was used in a limited number of patients for the treatment of MDR-Ab; further evaluation of its efficacy in larger numbers of patients is warranted.

Comparison of molecular typing methods for the analyses of Acinetobacter baumannii from ICU patients

Acinetobacter baumannii has emerged as an important cause of healthcare-associated infections causing great morbidity and mortality. Despite its clinical importance, it is still unknown which molecular typing method is the best to determine or confirm institutional outbreaks as well as to identify epidemiologically related isolates from different geographical areas. To determine the most discriminatory molecular typing method, we isolated A. baumannii from perianal swabs collected from intensive care unit (ICU) patients in a cohort study during 2002 and 2008. Strains from each year were analyzed by pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and multi-locus variable-number tandem repeat analysis (MLVA). Genetic relatedness of the isolates was consistent between PFGE and MLST as well as between analyses of loci containing MLVA and MLST. Our data show that PFGE and MLVA are similar when discriminating between isolates and are both good methods to use when questioning whether two isolates are indistinguishable.

Carbapenem resistant Pseudomonas aeruginosa and Acinetobacter baumannii at Mulago Hospital in Kampala, Uganda (2007-2009)

Background

Multidrug resistant Pseudomonas aeruginosa and Acinetobacter baumannii are common causes of health care associated infections worldwide. Carbapenems are effective against infections caused by multidrug resistant Gram-negative bacteria including Pseudomonas and Acinetobacter species. However, their use is threatened by the emergence of carbapenemase-producing strains. The aim of this study was to determine the prevalence of carbapenem-resistant P. aeruginosa and A. baumannii at Mulago Hospital in Kampala Uganda, and to establish whether the hospital environment harbors carbapenem-resistant Gram-negative rods.

Results

Between February 2007 and September 2009, a total of 869 clinical specimens were processed for culture and sensitivity testing yielding 42 (5 %) P. aeruginosa and 29 (3 %) A. baumannii isolates, of which 24 % (10/42) P. aeruginosa and 31 % (9/29) A. baumannii were carbapenem-resistant. Additionally, 80 samples from the hospital environment were randomly collected and similarly processed yielding 58 % (46/80) P. aeruginosa and 14 % (11/80) A. baumannii, of which 33 % (15/46) P. aeruginosa and 55 % (6/11) A. baumannii were carbapenem-resistant. The total number of isolates studied was 128. Carbapenemase genes detected were bla_IMP-like (36 %, 9/25), bla_VIM-like (32 %, 8/25), bla_SPM-like (16 %, 4/25); bla_NDM-1-like (4 %, 1/25) in carbapenem-resistant P. aeruginosa, and bla_OXA-23-like (60 %, 9/15), bla_OXA-24-like (7 %, 1/15), bla_OXA-58-like (13 %, 2/15), and bla_VIM-like (13 %, 2/15) in carbapenem-resistant A. baumannii. Furthermore, class 1 integrons were detected in 38 % (48/128) of P. aeruginosa and Acinetobacter, 37 % (26/71) of which were in clinical isolates and 39 % (22/57) in environment isolates. Gene cassettes were found in 25 % (12/48) of integron-positive isolates. These were aminoglycoside adenylyltransferase ant(4′)-IIb (3 isolates); trimethoprim-resistant dihydrofolate reductase dfrA (2 isolates); adenyltransferase aadAB (3 isolates); QacE delta1 multidrug exporter (2 isolates); quinolone resistance pentapeptide repeat protein qnr (1 isolate); and metallo-β-lactamase genes bla_VIM-4-like, bla_IMP-19-like, and bla_IMP-26-like (1 isolate each). Gene cassettes were missing in 75 % (36/48) of the integron-positive isolates.

Conclusions

The prevalence of carbapenem-resistant P. aeruginosa and Acinetobacter among hospitalized patients at Mulago Hospital is low compared to rates from South-East Asia. However, it is high among isolates and in the environment, which is of concern given that the hospital environment is a potential source of infection for hospitalized patients and health care workers.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2986-7) contains supplementary material, which is available to authorized users.

Guiding Empiric Treatment for Serious Bacterial Infections via Point of Care [Formula: see text]-Lactamase Characterization

Fever is one of the most common symptoms of illness in infants and represents a clinical challenge due to the potential for serious bacterial infection. As delayed treatment for these infections has been correlated with increased morbidity and mortality, broad-spectrum [Formula: see text]-lactam antibiotics are often prescribed while waiting for microbiological lab results (1-3 days). However, the spread of antibiotic resistance via the [Formula: see text]-lactamase enzyme, which can destroy [Formula: see text]-lactam antibiotics, has confounded this paradigm; empiric antibiotic regimens are increasingly unable to cover all potential bacterial pathogens, leaving some infants effectively untreated until the pathogen is characterized. This can lead to lifelong sequela or death. Here, we introduce a fluorescent, microfluidic assay that can characterize [Formula: see text]-lactamase derived antibiotic susceptibility in 20 min with a sensitivity suitable for direct human specimens. The protocol is extensible, and the antibiotic spectrum investigated can be feasibly adapted for the pathogens of regional relevance. This new assay fills an important need by providing the clinician with hitherto unavailable point of care information for treatment guidance in an inexpensive and simple diagnostic format.

Resistance patterns of multidrug resistant Acinetobacter baumannii in an ICU of a tertiary care hospital, Malaysia

Backgrounds & Objective:

Antimicrobial resistance is a major health problem worldwide in hospitals. The main contributing factors are exposures to broad-spectrum antimicrobials and cross-infections. Understanding the extent and type of antimicrobial use in tertiary care hospitals will aid in developing national antimicrobial stewardship priorities.

Methods:

In this study, we have analyzed the antimicrobial agents’ usage for acquisition of multidrug resistant using retrospective, cross-sectional, single-centre study in a multidisciplinary ICU at tertiary care hospital.

Results:

Acinetobacter baumannii (ACB) was isolated in various specimens from 662 patients. From these, 136 patients who were diagnosed with Ventilator-associated pneumonia (VAP) caused by ACB were included into the study. In our study, MDR strain accounts for 51% of all VAP cases caused by ACB. The development of ACB VAP were 10.5 + 6.4 days for MDR strains compared to susceptible organism (7.8 + 4.5 days) and had significantly longer ICU stay.

Conclusion:

The study concludes that prudent use of antimicrobial agents is important to reduce acquisition of MDR ACB.

A meta-analysis of in vitro antibiotic synergy against Acinetobacter baumannii

The aim of the work was to describe the different in vitro models for testing synergism of antibiotics and gather the results of antibiotic synergy against multidrug-resistant Acinetobacter baumannii (MDR-Ab). The different original articles were obtained from different web sites. In order to compare the results obtained by the different methods for synergy testing, the Pearson chi-square and the Fischer tests were used. Moreover, non-parametric chi-square test was used in order to compare the frequency distribution in each analysed manuscript. In the current meta-analysis 24 manuscripts, which encompassed 2016 tests of in vitro synergism of different antimicrobials against MDR-Ab, were revised. Checkerboard synergy testing was used in 11 studies, which encompasses 1086 tests (53.9%); time-kill assays were applied in 12 studies, which encompass 359 tests (17.8%); gradient diffusion methods were used in seven studies, encompassing 293 tests (14.5%). And, finally, time-kill plus checkerboard were applied in two studies, encompassing 278 tests (13.8%). By comparing these data, checkerboard and time-kill methods were significantly more used than gradient diffusion methods (p<0.005). Regarding synergy rates obtained on the basis of the applied method, checkerboard provided 227 tests (20.9%) with a synergistic effect; time-kill assays yielded 222 tests (61.8%) with a synergistic effect; gradient diffusion methods only provided 29 tests (9.9%) with a synergistic effect; and, finally, time-kill plus checkerboard yielded just 15 tests (5.4%) with a synergistic effect. When comparing these percentages, synergy rates reported by time-kill methods were significantly higher than that obtained by checkerboard and gradient diffusion methods (p<0.005). On the basis of the revised data, the combinations of a bactericidal antibiotic plus Tigecycline, Vancomycin or Teicoplanin are not recommended. The best combinations of antibiotics are those which include bactericidal antibiotics such as Carbapenems, Fosfomycin, Amikacin, Polymyxins, Rifampicin and Ampicillin/Sulbactam.

Emergence of Resistance inPseudomonas aeruginosaandAcinetobacterSpecies After the Use of Antimicrobials for Burned Patients

Objectives:

To evaluate the emergence of resistance ofPseudomonas aeruginosaandAcinetobacterspecies to imipenem, ciprofloxacin, or both after the use of these drugs and to compare resistant with susceptible isolates by molecular typing.

Design:

Cohort study.

Setting:

Burn intensive care unit (ICU) with 4 beds in a tertiary-care university hospital.

Methods:

During 16 months, surveillance cultures were performed for all patients admitted to the ICU. Demographic information was obtained for each patient. Molecular typing was done by pulsed-field gel electrophoresis using restriction enzymes for 71 isolates ofP. aeruginosaandAcinetobacterspecies.

Results:

Thirty-four patients were admitted and 22 were colonized by susceptibleP. aeruginosaorAcinetobacterspecies before they used the antimicrobials. Nine (41%) of these patients had a resistant isolate after antimicrobial use: 5 had used imipenem alone, 1 had used ciprofloxacin, and 3 had used both drugs. The interval between isolation of the susceptible and resistant isolates ranged from 4 to 25 days, but was 10 or more days for 6 patients. Molecular typing revealed that susceptible and resistant isolates from each patient were different and that although there were no predominant clones among susceptible isolates, there was a predominant clone among resistant isolatesof P. aeruginosaandof Acinetobacter.

Conclusions:

Resistance was not due to the acquisition of resistance mechanisms by a previously susceptible strain, but rather to cross-transmission. Although various measures involving antimicrobial use have received great attention, it would seem that practices to prevent cross-transmission are more important in controlling resistance.

Aggressive Control Measures for ResistantAcinetobacter baumanniiand the Impact on Acquisition of Methicillin-ResistantStaphylococcus aureusand Vancomycin-ResistantEnterococcusin a Medical Intensive Care Unit

The medical ICU implemented aggressive control measures following an outbreak of multidrug-resistant, clonalAcinetobacter baumannii.Multivariable regression analyses comparing acquisition (6 months preceding to 6 months during or following the outbreak) revealed decreased VRE and MRSA acquisition. Aggressive control measures can reduce VRE, and perhaps MRSA, transmission.

Nosocomial Outbreak of Infection With Pan–Drug-ResistantAcinetobacter baumanniiin a Tertiary Care University Hospital

Objective.

TO describe what is, to our knowledge, the first nosocomial outbreak of infection with pan–drug-resistant (including colistin-resistant)Acinetobacter baumannii,to determine the risk factors associated with these types of infections, and to determine their clinical impact.

Design.

Nested case-control cohort study and a clinical-microbiological study.

Setting.

A 1,521-bed tertiary care university hospital in Seville, Spain.

Patients.

Case patients were inpatients who had a pan-drug-resistantA. baumanniiisolate recovered from a clinical or surveillance sample obtained at least 48 hours after admission to an intensive care unit (ICU) during the time of the epidemic outbreak. Control patients were patients who were admitted to any of the “boxes” (ie, rooms that partition off a distinct area for a patient's bed and the equipment needed to care for the patient) of an ICU for at least 48 hours during the time of the epidemic outbreak.

Results.

All the clinical isolates had similar antibiotic susceptibility patterns (ie, they were resistant to all the antibiotics tested, including Colistin), and, on the basis of repetitive extragenic palindromic-polymerase chain reaction, it was determined that all of them were of the same clone. The previous use of quinolones and glycopeptides and an ICU stay were associated with the acquisition of infection or colonization with pan-drug-resistant A.baumannii.To control this outbreak, we implemented the following multicomponent intervention program: the performance of environmental decontamination of the ICUs involved, an environmental survey, a revision of cleaning protocols, active surveillance for colonization with pan-drug-resistantA. baumannii,educational programs for the staff, and the display of posters that illustrate contact isolation measures and antimicrobial use recommendations.

Conclusions.

We were not able to identify the common source for these cases of infection, but the adopted measures have proven to be effective at controlling the outbreak.

Clinical Features and Epidemiology ofAcinetobacter baumanniiColonization and Infection in Spanish Hospitals

Objective:

To investigate the clinical features and the epidemiology ofAcinetobacter baumanniiin Spanish hospitals.

Design:

Prospective multicenter cohort study.

Setting:

Twenty-seven general hospitals and one paraplegic center in Spain.

Methods:

All cases ofA. baumanniicolonization or infection detected by clinical samples during November 2000 were included. Isolates were identified using phenotypic and genotypic methods. The molecular relatedness of the isolates was assessed by pulsed-field gel electrophoresis.

Results:

Twenty-five (89%) of the hospitals had 221 cases (pooled rate in general hospitals, 0.39 case per 1,000 patient-days; range, 0 to 1.17). The rate was highest in intensive care units (ICUs). Only 3 cases were pediatric. The mean age of the patients in the general hospitals was 63 years; 69% had a chronic underlying disease and 80% had previously received antimicrobial treatment. Fifty-three percent of the patients had an infection (respiratory tract, 51%; surgical site, 16%; and urinary tract, 11%). Crude mortality was higher in infected than in colonized patients (27% vs 10%; relative risk, 1.56; 95% confidence interval, 1.2 to 2.0;P= .003). Molecular analysis disclosed 79 different clones. In most hospitals, a predominant epidemic clone coexisted with other sporadic clones. Imipenem resistance was present in 39% of the hospitals.

Conclusions:

A. baumanniiwas present in most participating Spanish hospitals (particularly in ICUs) with different rates among them. The organisms mainly affected predisposed patients; half of them were only colonized. Epidemic and sporadic clones coexisted in many centers.

Effect of carbapenem consumption patterns on the molecular epidemiology and carbapenem resistance of Acinetobacter baumannii

This study investigated the molecular epidemiology of Acinetobacter baumannii in the University of Debrecen in relation to antibiotic consumption. Overall and ward-specific antibiotic consumption was measured by the number of defined daily doses (DDD) per 100 bed-days between 2002 and 2012. Consumption was analysed against the number of A. baumannii positive patients per 100 bed-days, number of isolates per positive sample, and proportion of carbapenem resistant A. baumannii, using time-series analysis. Altogether 160 A. baumannii isolates from different wards were collected and analysed. Carbapenemase genes blaOXA-23-like , blaOXA-24-like , blaOXA-48-like , blaOXA-51-like , blaOXA-58-like and integrons were sought by PCR. Relatedness of isolates was assessed by PFGE. Prevalence and carbapenem resistance of A. baumannii were statistically associated with carbapenem consumption. Prevalence data followed carbapenem usage with three quarterly lags (r = 0.51–0.53, P<0.001), and meropenem and ertapenem, but not imipenem usage, affected prevalence. Colistin usage, in turn, lagged behind prevalence with one lag (r = 0.68–0.70, P<0.001). Six clusters were identified; the neurology ward with the lowest carbapenem consumption was associated with the carbapenem-susceptible cluster, as well as with the carbapenem-susceptible isolates in the cluster with variable susceptibility. Wards with high carbapenem usage almost exclusively harboured isolates from carbapenem-resistant clusters. All clusters were dominated by isolates of one or two wards, but most wards were represented in multiple clusters. Increases in prevalence and carbapenem resistance of A. baumannii were associated with usage of meropenem and ertapenem but not of imipenem, which led to the spread of multiple clones in the University.

Clonal diversity of Acinetobacter baumannii from diabetic patients in Saudi Arabian hospitals

Carbapenem-resistant Acinetobacter baumannii (CR-AB) represents a major health-care problem, causing high rates of morbidity and mortality. This study investigated the clonality of CR-AB isolated from diabetic patients from different regions in Saudi Arabia, as well as the relatedness of the β-lactamase genes. A total of 64 non-repetitive CR-AB clinical isolates were collected from 16 different regions in Saudi Arabia from intensive care patients. Isolates were identified phenotypically by the Vitek 2 compact system and genotypically by amplification of the bla OXA-51-like gene. The target sequences were amplified by PCR and the clonal diversity of the isolates was explored by PFGE. Resistance studies revealed that the prevalence of imipenem and meropenem resistance was 92 % and 96 %, respectively, while the vast majority of the isolates were susceptible to tigecycline and colistin. In addition, bla VIM and bla OXA-23 were the most prevalent genes in the isolates under investigation, while ISAba1 was the most dominant insertion sequence. PFGE results showed 13 clusters; clone H was dominant, comprising 20 isolates from four hospitals, followed by clones C and F, comprising 11 isolates each from three and six hospitals, respectively. Moreover, the current study signified the clonal diversity of CR-AB in Saudi Arabia and showed the ability of some clones to infect patients in many different cities.

Carbapenem-resistant Enterobacteriaceae and the correlation between carbapenem and fluoroquinolone usage and resistance in the US military health system

Whether carbapenem or fluoroquinolone usage is correlated with carbapenem-resistant Enterobacteriaceae (CRE) has not been investigated at the level of an entire US nationwide managed health care system. We analyzed 75 million person-years of surveillance and 1,969,315 cultures from all 266 hospitals in the geographically dispersed US military health system. Incidences of CRE remained under 1 case per 100,000 person-years. Incidences of CRE increased relative to 2005 baseline levels in 3 of 7 subsequent years, then decreased in 2012 (P<0.05). Incident proportions of carbapenem resistance (CR) differed significantly among years, geographical regions, and bacterial species. Although use and resistance strongly correlated (R>0.80) for several "drug-bug" combinations, none were significant at the national or facility level. One exception was that inpatient consumption of fluoroquinolones was significantly correlated (P=0.0007) with CR in Escherichia coli when data from the major referral centers of the Southern and Northern regions were combined.

Risk factors and outcomes of infections caused by extremely drug-resistant gram-negative bacilli in patients hospitalized in intensive care units

BACKGROUND

Extremely drug-resistant gram-negative bacilli (XDR-GNB) increasingly cause health care-associated infections (HAIs) in intensive care units (ICUs).

METHODS

A matched case-control (1:2) study was conducted from February 2007 to January 2010 in 16 ICUs. Case and control subjects had HAIs caused by GNB susceptible to ≤1 antibiotic versus ≥2 antibiotics, respectively. Logistic and Cox proportional hazards regression assessed risk factors for HAIs and predictors of mortality, respectively.

RESULTS

Overall, 103 case and 195 control subjects were enrolled. An immunocompromised state (odds ratio [OR], 1.55; P = .047) and exposure to amikacin (OR, 13.81; P < .001), levofloxacin (OR, 2.05; P = .005), or trimethoprim-sulfamethoxazole (OR, 3.42; P = .009) were factors associated with XDR-GNB HAIs. Multiple factors in both case and control subjects significantly predicted increased mortality at different time intervals after HAI diagnosis. At 7 days, liver disease (hazard ratio [HR], 5.52), immunocompromised state (HR, 3.41), and bloodstream infection (HR, 2.55) predicted mortality; at 15 days, age (HR, 1.02 per year increase), liver disease (HR, 3.34), and immunocompromised state (HR, 2.03) predicted mortality; and, at 30 days, age (HR, 1.02 per 1-year increase), liver disease (HR, 3.34), immunocompromised state (HR, 2.03), and hospitalization in a medical ICU (HR, 1.85) predicted mortality.

CONCLUSION

HAIs caused by XDR-GNB were associated with potentially modifiable factors. Age, liver disease, and immunocompromised state, but not XDR-GNB HAIs, were associated with mortality.

Surveillance and correlation of antimicrobial usage and resistance of Pseudomonas aeruginosa: a hospital population-based study

This retrospective study evaluated trends and association between resistance of Pseudomonas aeruginosa isolated from patients with hospital-acquired infections (HAIs) and hospital antimicrobial usage from 2003 through 2011 in a tertiary care hospital in northeast China. HAI was defined as occurrence of infection after hospital admission, without evidence that infection was present or incubating (≦48 h) on admission. In vitro susceptibilities were determined by disk diffusion test and susceptibility profiles were determined using zone diameter interpretive criteria, as recommended by Clinical and Laboratory Standards Institute (CLSI). Data on usage of various antimicrobial agents, expressed as defined daily dose (DDD) per 1,000 patients-days developed by WHO Anatomical Therapeutical Chemical (ATC)/DDD index 2011, were collected from hospital pharmacy computer database. Most of 747 strains of P. aeruginosa were collected from respiratory samples (201 isolates, 26.9%), blood (179, 24.0%), secretions and pus (145, 19.4%) over the years. Time series analysis demonstrated a significant increase in resistance rates of P. aeruginosa to ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoperazone/sulbactam, piperacillin, imipenem, meropenem, ceftazidime, cefepime, ciprofloxacin, and levofloxacin except aminoglycosides over time in the hospital (P<0.001). The rates of carbapenem-resistant P. aeruginosa (CRPA) isolated from patients with HAIs were 14.3%, 17.1%, 21.1%, 24.6%, 37.0%, 48.8%, 56.4%, 51.2%, and 54.1% over time. A significant increase in usage of anti-pseudomonal carbapenems (P<0.001) was seen. ARIMA models demonstrated that anti-pseudomonal carbapenems usage was strongly correlated with the prevalence of imipenem and meropenem-resistant P. aeruginosa (P<0.001). Increasing of quarterly CRPA was strongly correlated at one time lag with quarterly use of anti-pseudomonal carbapenems (P<0.001). Our data demonstrated positive correlation between anti-pseudomonal antimicrobial usage and P. aeruginosa resistance to several classes of antibiotics, but not all antimicrobial agents in the hospital.

Biologically inspired strategies for combating bacterial biofilms

Infections caused by bacterial biofilms are a significant global health problem, causing considerable patient morbidity and mortality and contributing to the economic burden of infectious disease. This review describes diverse strategies to combat bacterial biofilms, focusing firstly on small molecule interference with bacterial communication and signaling pathways, including quorum sensing and two-component signal transduction systems. Secondly we discuss enzymatic approaches to the degradation of extracellular matrix components to effect biofilm dispersal. Both of these approaches are based upon non-microbicidal mechanisms of action, and thereby do not place a direct evolutionary pressure on the bacteria to develop resistance. Such approaches have the potential to, in combination with conventional antibiotics, play an important role in the eradication of biofilm based bacterial infections.

The use of platensimycin and platencin to fight antibiotic resistance

Infectious diseases are known as one of the most life-threatening disabilities worldwide. Approximately 13 million deaths related to infectious diseases are reported each year. The only way to combat infectious diseases is by chemotherapy using antimicrobial agents and antibiotics. However, due to uncontrolled and unnecessary use of antibiotics in particular, surviving bacteria have evolved resistance against several antibiotics. Emergence of multidrug resistance in bacteria over the past several decades has resulted in one of the most important clinical health problems in modern medicine. For instance, approximately 440,000 new cases of multidrug-resistant tuberculosis are reported every year leading to the deaths of 150,000 people worldwide. Management of multidrug resistance requires understanding its molecular basis and the evolution and dissemination of resistance; development of new antibiotic compounds in place of traditional antibiotics; and innovative strategies for extending the life of antibiotic molecules. Researchers have begun to develop new antimicrobials for overcoming this important problem. Recently, platensimycin - isolated from extracts of Streptomyces platensis - and its analog platencin have been defined as promising agents for fighting multidrug resistance. In vitro and in vivo studies have shown that these new antimicrobials have great potential to inhibit methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and penicillin-resistant Streptococcus pneumoniae by targeting type II fatty acid synthesis in bacteria. Showing strong efficacy without any observed in vivo toxicity increases the significance of these antimicrobial agents for their use in humans. However, at the present time, clinical trials are insufficient and require more research. The strong antibacterial efficacies of platensimycin and platencin may be established in clinical trials and their use in humans for coping with multidrug resistance may be allowed in the foreseeable future.

Post-Neurosurgical Meningitis Due to Multidrug-ResistantAcinetobacter baumaniiTreated with Intrathecal Colistin: Case Report and Review of the Literature

Intrathecal colistin (Polymxin E) is becoming an important option for the treatment of post-neurosurgical meningitis caused by multidrug resistant (MDR) Acinetobacter baumannii. We report a case of 28-year-old man who developed meningitis due to MDR A. baumannii associated with an external ventricular drain. The patient was cured using a 4-week course of intrathecal colistin 3.2 mg via external ventricular drain (EVD) daily without any serious side effects.